When talking about the service life of PV systems, the same figure almost always comes up:
👉 0.5% power loss per year.
This value comes from meta-studies conducted by Fraunhofer ISE and NREL and describes the average annual power loss of individual silicon modules. Modern PV modules are therefore impressively stable.
In fact, in our tests we repeatedly see older PV modules that—provided there are no defects such as cell cracks, hot spots, or insulation problems—exhibit significantly lower power losses. In some cases, the measured degradation rates are even well below 0.5% per year, which shows how durable and robust high-quality modules actually are when operated under controlled conditions.
However, this value is often misunderstood:
He does not describe how much an entire system loses in performance over the years.
This is because a PV system does not consist of a single module, but rather thousands of components that interact with each other electrically, thermally, and mechanically.
1. Module degradation: The physical basis
“Module degradation” refers to the long-term, irreversible loss of performance of a PV module due to cell aging, UV radiation, moisture, and thermal cycles.
Fraunhofer and NREL studies show median values of 0.5–0.6% per year—in some cases even lower. That is the component perspective.
Measurements are always taken under controlled laboratory conditions or at selected reference fields.
2. Plant degradation: The reality in the field
In practice, however, what counts is the actual energy output at the feed-in meter—and this is influenced by far more than just module aging.
Here we are talking about the performance loss rate (PLR), i.e. the total annual degradation of a PV system.
This includes, among other things:
- Mismatch due to unequal module characteristics
- Contact and transition resistances (e.g., due to connectors)
- Hotspots, cell ruptures, PID effects
- Insulation faults and leakage currents
- Cable aging and corrosion
- Soiling
- Inverter and sensor drift
In the field, the PLR is therefore often between 0.8 and 1.2% per year, and in some cases significantly higher—especially if the installation or maintenance quality is not up to standard.
3. The weakest link determines the current
In a string, modules are almost always connected in series.
This means that all modules carry the same current, limited by the weakest module.
A single defect, e.g., a
- Microcrack,
- Hotspot,
- Contact problem or
- faulty plug,
can significantly reduce the performance of the entire string.
Bypass diodes protect the module, but at the same time they “cut off” partial currents.
This is how the classic scenario arises: a defective module pulls down the entire string.
4. Connectors and cables – the invisible weak point
Studies such as the HelioVolta PV Health Report 2025 show:
- Contact problems occur in over 80% of the systems inspected.
- 70% of EPCs fail to meet assembly or crimp specifications
-
Transition resistances, faulty crimps, or incompatible connectors cause
Power losses, hotspots, and, in extreme cases, fire risks
These electrical details are inconspicuous—but they determine whether a system delivers 10% more or less yield.
5. Plant degradation is a craft
The service life of modern modules is no longer a limitation today.
The following factors determine performance:
- Assembly quality and documentation
- Regular O&M checks
- Measurement and testing concepts that reveal errors at an early stage
System degradation is not inevitable—it is the cumulative result of many small technical details.
6. How 2nd Cycle solves the problem
This is exactly where 2nd Cycle comes in:
Our technology not only enables PV modules to be cleaned, but also thoroughly tested—electrically, visually, and in terms of safety.
Our core competencies:
- Performance testing & EL analysis: Identification of weak modules, hotspots, PID effects
- Insulation and breakdown tests: Identifying safety risks
- Plug replacement & electrical refurbishment: elimination of increased contact resistance
- Classification according to reusability: → “Fit for reuse” or “Recycling required”
- Automated cleaning & visual inspection
And all of this is also available as a mobile solution:
With the SolarBox, our mobile refurbishing unit, 2nd Cycle can inspect, clean, and select panels directly at the solar park.
The result:
✅ Reduced string mismatch losses
✅ Guaranteed electrical safety
✅ Maximum energy yield with minimal downtime
✅ Data-based decision between reuse or recycling
7. Conclusion
Module degradation is physics—stable, measurable, predictable.
Plant degradation, on the other hand, is a matter of craftsmanship, maintenance, and quality assurance.
2nd Cycle closes precisely this gap:
We ensure that an “average” PV system is transformed back into a high-performance, tested, and safe system—whether through stationary testing processes or mobile park refurbishing solutions directly on site.
Because sometimes even a weak connection is enough to lose thousands of euros in revenue -
but refurbishing it to win him back.
Suspected performance losses in your PV portfolio? Our automated testing technology provides you with clear data before yields are lost. – speek to us!